Call transmitter



Dec. 22, 1942. B. F. I Ewls CALL TRANSMITTER Filed Des. 4, 1940 2 sheets-'sheet 1 V. U2 Rnb n u mW W NE A (U. EL 5 3 Vfl. i 7 n 6. W 7 ma 4 u 2 l M 2 P A m G sx/ lmfr .I l ,\v|l 2 T l W C b w 2 3 G 2 F M.,

Patented Dec. 22, 1942 UN l TE D STATES PATENT 'al 0F FI f 2,306,068

CALL TRANSMITTER,

v Benjamin F. Lewis, Bayside, N. Yaassignorn to Bell Telephone'v Laboratories,v Incorlmrated, New York, N.'Y., a corporation' ofNew York Application December 4, 1940";SerialNoi1368Q438 6 Claims.

This invention relates to call transmitters of the type used in automatic telephone systems for controlling the operation of switches for establishing talking connections.

The object of the invention is to provide a call transmitter of the type above referred to, which will be simple to operate, positive in operation,

and which will effect a material reduction in thev time of transmitting any given telephone designation as compared to call transmitters now in use.

According to the invention, a set of manually operable key members numbered to represent digits isaprovided for operating in combination a number of vibrating reeds extending through the coil of lan electromagnetic device connected to the telephone line. These reeds form part of the electromagnetic device and are tuned to different frequencies for generating alternating currents of these frequencies in the telephone line to which the coil is connected and to thereby energize electrical filter devices placed at the exchangefor `selectively operating electromagnets which, in turn, control the operation of associated switches for establishing telephone connections corresponding to the digit key members which have been operated.

More specifically, a'ieature kci the invention resides in the plucking mechanism'by which the keys pluck the reeds directly instead of through an intermediate set of code bars as is the present practice, thus eliminating the 'code bars and allowing a more compact mechanism. In order lto do this, the call transmitter lof my invention uses a reed bank of eleven instead of ve reeds, the same being arranged so that digit code can be produced by plucking pairs of adjacent reeds. The reeds normally are deflected against a stop by suitable damping bars which are held against the' reeds by non-linear springs of the convex strip type. In one embodiment of the invention, each reed has an individual latch. When a key is pressed, the plunger rst depresses two adjacent damping barswhich allows the two reeds to rest on their latches, they, however, still being in a deflected position. Further movement of the key causes the two latches to be operated whereby the reeds slip off the latches and vibrate, the variations produced thereby in the magnetic eld induce the corresponding yalternating voltages in the pick-up coil. When the key is released, the damping bars press the yreeds .against the stop and the latch springs move the latches into their normalpositions.` The` non-'linear springs pro# -pos'sibility of 'Y partial operation of' lthe .keys

i" Other features -aindadvantages of the invention will A appear tfrornl the'. following description yand by theI-claims appendedthereto, reference being had to thevaccompanying drawings, inwhich:

Fig. 1 is a side .v-iew of the call `transmitter' of the invention disposedlwit-hin a telephone instrument `casing v'with arportion of the icasingcut away. Y

' Fig. v271s altopassembly viewwithv top key plate (which isshown in its entirety inEig. 7) partially cut` awaytoexpose the? disposition of reedvassembly;

-Fig.f3 is a side view ofthec'all transmittersimilar to Fig. 1 but showing the relation ofthe various parts of the mechanism when a numerical key is partially opera-ted;

Fig. 4 is a side yView similar'to Fig. 3 but showing the rela-tion of thevarious parts of the-mechanism when a numerical. key is-full-y operated;

Fig. 5 is a side VieWs-i-milar to Fig'. 1 of a modication of the invention;

Fig. 6 is -a top view similar to Fig. 210i said modification; and

Fig. 7 isa viewV of the key plate.

In 'order to simplify the description of the in- Vention,the same is disclosed-for inclusion within the telephoneinstrumen't housing shown and described in Patent 2,147,710 `granted to- R. F. Mallina on Februaryl 2-1, 1939,-and reference is made'theretofor a-complete description of such parts ofthe apparatus which are either yomitted or partially `described her-ein.` It is understood,

'r however,` that the inventionv isnot limited for application to telephone instrument housings of the kind vdescribed in theabo've-identied patent, it being readily evident toy anyone skilled'in the art that the same may be' easily adapted 'for use with other anddifferent types ofv -station equipment or may be usedseparately `and independ ently of any'station'equipment whatever,

Referring nowy to Figs. l-to 4,- inclusive, in which identical designations refer to identical parts in'all the figures, the base plate 20 cooperates with the casing 2| to form a housing for the callltransmitter mechanism and a cradle portion- 24 for the telephone handset (not shown), the casing 2| being secured to theY base 20 in the manner shown in the above-identied patent.

Onthe base plate 20 is also mounted ordinary switchhook springs (not shown) for operationl by plungers 23 upon` placing the -handset in the cradle portion 24' of the casing 2 i; and aringing device *is* mountedfon a supporting `frametherewithin which, in turn, is secured to the plate 2l!A also in the manner shown in the above-identified patent.

On the base plate 20 is mounted a support 45 upon which are mounted in superposed relation to each other, the rectangularly shaped permanent magnets PMI and PM2 between which the eleven vibrating reeds RI-RI and the plates 46 and 41 are clamped by screws SCS while the magnet and reed assembly thus formed is held on the support 45 by screws SCA and SCB, the plates 46 and 41 having their front edges formed diagonally to clamp diierent lengths of reeds in order'to obtain different vibrating periods. On the front of the pole-piece 5I is located the damper plate I which is coextensive with the length of the pole-piece aligned therewith and secured thereto by screws 53. The pole-piece 52 is not provided with a damper plate and, therefore, the lower screws 53 merely secure the pole-piece to the magnet.

The eleven reeds RI-RI in which identically designated reeds have identical periods, extend through an oblong-shaped opening of a coil 50 for movement adjacent the pole-pieces 5I and 52 which serve, in cooperation with the screws 53, spacer members 60 and 6I and damper plate I of magnetic material, for clamping the coil 5D on the front faces of magnets PMI and PM2, the terminal wires (not shown) of the coil being brought to the rear of the transmitter in any suitable manner.

Two U-members 5 are provided as a key support to the top of which is mounted the key plate I0 secured thereto by screws 3. The members 5 are clamped to the base plate 20 by screws 5 and are provided with aligned apertures through which is supported the damper rod 3 and the latch bar I0.

The free ends of the eleven reeds RI--RI are disposed normally to rest on damping bars DI- DII ofwhich one is providedfor each reed and which are pivotally supported upon rod 9. One end of each of these bars has a downwardly eX- tending hooked portion 2 the inner end of which engages the outer end of the correlated non-linear spring 3 clamped by screws 4 and 4 and clamping plate I I to the lower shelf of support 45, while the other end is formed into upwardly extending bent portions 2A and 2B to allow the bar to clear the clamping plate II when operated in the vmanner described hereinafter.

Aligned beneath each reed is a latch member such as LI pivotally supported upon latch-bar I0 and yieldably held with its vertical arm I2 against the latch stop bar I3 by the spring I4 which is anchored at one end to the associated damper bar such as DI and has its other end engaged under the horizontal arm of the latch member.

Each key KI, K2, K3, etc., consists of a cylindrically shaped button secured at the upper end of an offset plunger I5 having its lower end formed with a cross-member I'I which, when the key is normal, just clears the two damping bars such as DI and D2 oppositely disposed on either side of the plunger. The left cross-piece of the plunger is provided with a horizontal bar I6 which is suiilciently long to engage the horizontal arms of two adjacent latch bars such as LI and L2 disposed on either side of the plunger and, when the key is depressedsuiliciently for the plunger I5 to engage the damping bars DI, there is still a slight clearl ance between the lower face of the bar IB and the upper faces of the horizontal arms of the latch members. The keys are guided in their downward and upward movement by a face plate II engaging the cylindrically shaped buttons and a plate I 0 engaging the plunger portions of the keys, sai last-mentioned plate being secured to the two U-members 5 by the screws 8 as previously mentioned.

The keys are held in their non-operated position by compression springs 'I5 each having one of its ends abutting against the under-side of the oiset portion of the key plunger and its other end abutting the top surface of guiding plate '10.

In the operation of the invention, it may be assumed that the eleven reeds RI--RI are so disposed in relation to the keys KI-KU that the depression of the keys in the order given below will result in the plucking of the paired reeds indicated to produce the two frequencies identied by the subscripts to the reed designations. These irequencies, according to the following signal code, characterize the digit indicated by the key subscripts:

Digit desigmated The reeds RI-RI are normally deflected against the lower edge of the damper plate I by the corresponding damping bars Dl-DL under the tension of springs 3 and the vertical stop arms I2 of the corresponding latch members LI-LII are held against the stop bar I3 by the springs I4. When a key is depressed, the lower member Il at the end of plunger I5 depresses two adjacent damping bars which allows the two reeds to rest on their respective latches as disclosed in Fig. 3. Further movement of the key, as disclosed in Fig. 4, will cause the ends of the upper cross-piece I6 attached to this plunger I5 to engage the horizontal arms of the two associated latches whereby the latches are given a clockwise turn which causes the two reeds to slip oi the arms I2 of the latches. The reeds then vibrate and the variations in the iiux induce corresponding alternating current voltages in the coil 50.

When the key is released, the damping bars press the reeds against the stop I and the latch springs I4 move the latches into normal posi tion. The non-linear springs 3 provide a breakthrough action that limits the possibility of partial operation of the keys.

In the modification of the invention shown in Figs. 5 and 6, one damping bar D and one nonlinear spring 3 are used for all the reeds instead of one bar and spring for each reed. The damping bar map be a solid plate having the rectangular portion D, the upwardly bent portion 'I and the depending stud I8 which rests on the convex surface of the spring which, in turn, is held in position by the two stops 22 and 23 and suitable anchors 24 and 25 (nearer one, 25, not shown) in the base 20. In the rnodied form of the invention the key plungers do not need a lower cross-piece I'I for engaging two oppositely disposed dampers, inasmuch as the downward movement of any plunger will engage but the one damping plate.

In operation, the movement of any key plunger swings the damping plate counter-clockwise from the support 9, presses against spring 3 and aeoaoes thus causes all the reeds to come to rest in their respective latch arms i2. Since any one key plunger, in its further movement, controls but the two latches disposed oppositely on either side of the plunger cross-piece i only the two associated reeds will leave their respective positions of rest on their associated latches and start vibrating to produce the desired frequencies. The release of the key will cause the damping bar D to assume its normal position, being driven therem to by the tension of the spring While I have described my invention and the means for utilizing the same in connection with one speciiic embodiment thereof, it is to be understood that various other applications embodiments thereof may be by those skilled in the art without departing from the spirit of the invention as defined within the scope oi the appended claims.

What is claimed is:

l. In a call transmitter, a plurality oi operable digit key members, a plurality ci pretensioned reeds arranged in pairs, each one of said key members being operatively associated with a diiferent one of each of said pairs of reeds, and means responsive to the operation of any one of sai-d key members to cause the operation of its associated pair of reeds for setting them into vibration.

2. In a call transmitter, a plurality oi operable digit key members, a plurality oi reeds arranged in pairs, each one of said key members being operatively associated with a different one of said pairs of reeds, a pivoted bar for each of said reeds, each of said bars being normally disposed to hold the associated reed under tension, and means responsive to the operation of any one of said key members for operating two of said bars whereby the associated pair of reeds are released from tension and set into vibration.

3. In a call transmitter, a plurality of operable digit key members, a plurality of reeds arranged in pairs, each one of said key members being operatively associated with a different one of each of said pairs of reeds, a piyoted bar for all of said reeds, said bar being normally disposed to hold all of said reeds under tension, means responsive to the operation of any one of said digit key members for operating said bar to release the tension on said reeds, and other means responsive to the operation of said digit key memlil ber for setting its pair of associated reeds into vibration.

4. in a call transmitter, a plurality of operable digit key members, a plurality of reeds arranged in pairs, each one of said key members being operatively associated with a different one of each of said pairs or reeds, a plurality of means normally holding all of said reeds in pretensioned positions, and means responsive to the operation oi any key member for actuating two oi said means whereby the pair of reeds associated with sai-d operated key member is set in vibration,

5. lin a call transmitter, a plurality of operable digit key members, a plurality of reeds dispos d in groups of two, one reed on each side of each oi said key members, a plurality of bars normally holding said reeds in pretensioned position and operably controllable in sets of two by each of said digit key members, a pivoted latch intermediate each reed and bar, and a spring intermediate each latch and bar whereby the partial depression of any key member operates the associated set oi two bars to release the correlated reeds from their pretensioned position and whereby the full depression of said digit key member operates the associated latches to pluck the associated reeds, said spring intermediate each operated latch and bar servingrto restore the associated latch to its normal position upon the restoration of said operated key member.

6. In a call transmitter, a magnet, a plurality ci operable digit key members, a plurality of reeds disposed in groups of two, one on either side of each or" said key members, a stop member for each reed disposed upon said magnet in vertical alignment with the associated reed, a bar for each reed, said bars being actuatable in groups of two by each of said key members, each of said bars being normally disposed to hold the associated reed in a pretensioned position against the associated stop member, and a pivoted latch for each reed disposed in vertical alignment thereunder, whereby a partial depression of a key member operates two bars to release the two associated reeds from their pretensioned position against their stop members and whereby a full depression or said key member operates the two latches correlated with said operated two bars to pluck the associated reeds into vibratory action.

BENJAMIN F. LEWIS. 

